This invention relates generally to gas turbine engines and more particularly to tube coupling assemblies for use in connecting fluid tubing in gas turbine engines.
Gas turbine engines such as those used for aircraft propulsion generally include external tubing systems for delivering fluids, such as jet fuel, hydraulic fluid and lubricating oils, from one engine component to another or for connecting an engine component with an aircraft system. These tubing systems typically include tube coupling assemblies (often referred to as tube fittings) to connect adjacent fluid-carrying tubes or to connect a tube to another engine component. In an aircraft engine, a leak of a flammable fluid could result in a fire and/or loss of power which would jeopardize the safety of the aircraft flight. Thus, the primary requirement of any tube coupling assembly is that it not leak.
Various types of coupling assemblies or tube fittings have been employed in the aircraft engine industry to effect leak proof connections. One prior tube coupling assembly which has been commonly used in gas turbine engines is the ballnose fitting. A ballnose fitting typically comprises a tube connector connected to a first fluid-carrying tube, a ferrule connected to a second fluid-carrying tube and a coupling nut having internal threads which engage external threads on the tube connector so as to urge the tube connector and ferrule against one another in sealing engagement, thereby forming a single sealing element. Such single element fittings often employ shrouds with drain systems to contain any leakage which may occur.
Although single element fittings have been used advantageously in a number of gas turbine engine applications, they are subject to certain limitations. For instance, it is believed that shrouds and drain systems not only add to the complexity of the engine construction, thereby increasing expense and maintenance time, but also increase the weight of the engine.
Accordingly, there is a need for a tube coupling assembly which eliminates the need for shrouds and drain systems while providing excellent sealing integrity.